Method and apparatus for improving car rollability in a railroad classification yard

ABSTRACT

A method and apparatus for improving the rollability of railroad cars moving into a classification yard or into the straight storage sections of the classification tracks of a classification yard; at least two wheels on each truck of each car are engaged by a guide rail which may be a part of a small retarder and which extends parallel to the track. The guide rail forces the wheels, and hence the truck, into alignment with the track. As applied to storage tracks, the track is preferably inclined, through the length encompassing the guide rail, at an angle sufficient to compensate for any loss of kinetic energy due to the limited braking effect of the guide rail.

United States Patent Frank [111 3,815,508 June 11, 1974 METHOD ANDAPPARATUS FOR IMPROVING CAR ROLLABILITY IN A RAILROAD CLASSIFICATIONYARD Inventor:

[1.8. CI. 104/26 R, 246/182 A Int. Cl B6lb 1/00 Field of Search"...246/182 A; 104/26 R, 26 A;

References Cited UNITED STATES PATENTS 2/l930 Kramer 188/62 4/1932 Howe188/62 2.499.812 3/1950 Beltman 188/62 3,234,378 2/1966 Gallacher246/182 A FOREIGN PATENTS OR APPLICATIONS 1,375,879 /1964 France 246/182A 4 Primary Examiner-Gerald M. Forlenza Assistant Examiner-George H.Libman Attorney, Agent, or Firm-James B. Kinzer; Thomas E. Dorn 5 7ABSTRACT A method and apparatus for improving the rollability ofrailroad cars moving into a classification yard or into the straightstorage sections of the classification tracks of a classification yard;at least two wheels on each truck of each car are engaged by a guiderail which may be a part of a small retarder and which extends parallelto the track. The guide rail forces the wheels, and hence the truck,into alignment with the track. As applied to storage tracks, the trackis prefer ably inclined, through the length encompassing the guide rail,at an angle sufficient to compensate for any loss of kinetic energy dueto the limited braking effect of the guide rail.

8 Claims, 4 Drawing Figures 43 44 a3 45 40 4s 46 56 I 56 53 53 $447 74-4-4 7 4 FROM 1 42 '49 l I 25 A CURVE 24 4 47 33 52 I TO BRAKE 26 a 7 ll PATENTEDJUNI 1 I974 SHEET 2 BF 2 FIGB l 1O. 19 O 18 0 0 |6. O O 1 o LE A G M N R A O R 2 N I. O m

ROLLING RESISTANCE FIG.4

BACKGROUND OF THE INVENTION In a railroad classification yard, therollability characteristics of the cars beingclassified play' animportant part in determining the efficiency of the classificationoperation. For example, acar with extremely high rollability may tend toaccelerate through the yard to an excessive extent, and may couple toother cars on a storage track at an excessive speed. Suchhigh-rollability cars occur infrequently, and can usually be maintainedin good control by the provision of adequate re tarder facilities in theyard. On the other hand, a car of extremely poor rollability may stallbefore it reaches the end of a classification track, causing anexcessive impact when engaged by the next car moving down the sametrack. v

In many classification yards, particularly those in which braking'iseffected on distribution or group tracks ahead of the actualclassification tracks, braking is controlled in accordance with therolling resistance of the individual cars. The rolling resistance of agiven car is affected by many different factors, including theconstruction of the car trucks, irregularities in the classificationyard tracks, curves and turnouts in the tracks, the release speed of thecar at the top of the yard hump, air friction, wind, temperaturevariations, rain, snow, dirt and other factors In many yards, an attemptis ing the friction at the interface between the car wheel flanges andthe rails. A car which 'is a poor roller to mide to compute therollingresistance of each cut of cars before braking in order toestablish a safe and effective release speed for the cars. Thecharacteristics of given individual tracks may be taken into account inmaking this computation. However, controls of this nature are not alwaysreliable because the rolling resistance for a given car or cut of carsmay vary widely depending on whether the cars are accelerating ordecelerating, have been moving or are moving on curved or straighttracks, or are subject to other variable factors.

In some classification yards, in which each classification track in theyard is equipped with an individual controllable retarder, thesevariations in'car rollability do not play such an important part. Thisis true primarily because the braking point is much nearer the ultimatecoupling point on the storage track and the cars are not subject to someof the major rollability variation factors, including grade changes,curves, turnouts and the like. In yards of this nature, most cars can beeffectively controlled on the basis of relatively simple speedmeasurements without requiring an actual computation of rollingresistance. Even in a yard of the latter type, however, cars exhibitingextremely high rolling resistance can interfere with efficient andconsistent yard operation at a high classification rate. This isparticularly true of cars for which rollability may. change markedlyfrom the time of entry into the yard to the time of movement onto agiven storage track.

One factor materially affecting rollability, which can cause substantialdifficulty in the operation of any classification yard, results from thepresence of the curves in the track ahead of the yard and in the trackrequired to transfer cars from the hump track to the individualclassification tracks. A railroad car moving around a curve inherentlytends to come out of the curve with the trucks of the c'armisaligned,substantially increasbegin with, when coming out of a curve, is likelyto be moving so slowly as to require no braking. Under thesecircumstances, even though there may be a retarder on the classificationtrack, the car wheels remain out'of alignment. Moreover, braking wouldbe undesirable, tending to slow the car even more and quite possiblystalling the car in the retarder with potentially disastrous results.Consequently, even in a well-designed yard it may be necessary to limitoperational speeds to compensate for poor rolling cars, reducing theefficiency and capacity of the yard to a' marked extent.

SUMMARY OF THE INVENTION A further object of the invention is to providea new and improved method and apparatus for aligning the trucks on eachcar moving into a classification track,

parallel to the track, without substantial reduction in the kineticenergy of the cars.

A specific object of the invention is to provide a new and improvedmethod and apparatus for operation of a classification yard of thekind-having a controllable retarder in each classification track, theimprovement comprising means for aligning the trucks on each carparallel to the track when each car enters the yard and re-aligning thetrucksafter the car has traversed the last curve on each classificationtrack and has entered the straight storage section of the track butbefore the car reaches the retarder that determines the final releasespeed forthe car.

A specific object of the invention is to increase the efficiency andoperational rate for a railroad classification yard by assuring maximumrollability for each car moving into the storage sections of theclassification tracks of the yard, utilizing apparatus that is simple innature and relatively inexpensive to construct, and that requires aminimum of maintenance.

In its method aspect, the invention relates to a method for improvingthe rollability of railroad cars during classification operations in arailroad classification yard of the kind in which individual cars orcuts of cars are releasedfrom a hump location and roll, by gravity, downan inclined hump track and thence down a classification track whichincludes a transition section comprising at least one curve leading intoa straight storage section. The method of the invention comprisespositively engaging at least two wheels on each truck of each car,simultaneously, to align each car truck parallel with the storagesection of the classification track after the car has completelytraversed the curved tran sition section of the classification track andbefore the car has moved any substantial distance down the straightstorage section of the track.

In its apparatus aspect, the invention relates to an improvement in agravity-operated railroad classification yard of the kind including ahump, a hump track inclined downwardly from the hump, a plurality ofclassification tracks connected to and inclined downwardly from the humptrack, with each classification track comprising a curved transitionsection leading into a straight storage section, and retarder meansforbraking each car as the car traverses the yard between the hump andthe storage sectionof one of the classification tracks. The improvementof the invention. comprises a plurality of truck aligning means, onelocated at the upper end of the storage section of eachclassificationtrack, for aligning each truck of each car in parallel relation to thestorage section of the associated classification track. Each truckaligning meanscomprises an elongated guide rail, long-enough to engageat least two wheels on each car truck, positioned parallel to the flangeside of the classification track storage section and close enough to thetrack to engage the flange side of each car wheel traversing theclassification track.

BRIEF DESCRIPTION or THE DRAWINGS FIG. 1 is a simplified plan view of apart of a gravityoperated railroad classification yard modified toincorporate the present invention; I

FIG. 1A is a gradient profile of one of the classification tracks in theyard of FIG. 1;

FIG. 2 is a schematic plan view of the trucks of two railroad cars,utilized to explain the operation of the invention; g

FIG. 3 is a plan view of a single car truck entering truck-aligningmeans in accordance with the present invention; and I I FIG. 4 is achart of the distributionof rolling resistance characteristics forrailroad cars in general.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a plan view of aclassification yard modified to operate in accordance with the method ofthe present invention and incorporating car truck alignment apparatusconstructed in accordance with a preferred embodiment of the invention.Classification yard 10 comprises a downwardly inclined hump track 11,leading into the yard from an elevated hump 7t). Hump track 11 branchesinto a distribution track l2which in turn branches into a series ofclassification tracks 21, 22, and 23. It will be understood that theclassification yard 10 would ordinarily include'many more suchclassification tracks; only three classification tracks have been shownin FIG. 1 because these are adequate to afford an effective descriptionof the invention.

Classification track 22 is typical of the classification tracks in yard10. It comprises a curved transition section 24 extending from a switchon the distribution track [2 and leading into a straight storage section25. A car retarder 26 is located near the upper end of classificationtrack 22, on the straight storage section 25 of the track. The storagesection 25 of track 22 extends beyond retarder 26 for a substantialdistance to afford a storage area for a large group of cars being madeup into atrain. a

Classification track 21 issimilar to track 22. It includes a curvedtransition section 27 leadingfrom distribution track 12 into a straightstorage section-28. A car retarder 29 is located on the straight storagesection 28 of track 21, not far from the juncture of the curvedtransition section 27 with the straight storage section 28. Retarders 26and 29 may be conventional weightresponsive track brakes, and arepreferably provided with speed-responsive braking controls.

FIG. 1A illustrates the gradient profile for classification track 22,together with a part of distribution track 12 and hump track 11. Theincoming end of the track profile, at the left of FIG. 1A, which extendsfrom hump 70 along track 11 through distribution track 12 and throughthe curved transition section 2 4 of classification track 22 (FIG. 1),is of relatively constant grade. The grade selection is made inaccordance with the average rolling resistance for most of the cars thatwill be handled bythe yard. The distribution of rolling resistance amongAmerican railroad cars is generally illustrated in FIG. 4. Therollability or rolling resistance for with the expression:

in which: I

-h velocity head (translational head), in feet. H energyhead in feet.

w weight of car wheels and axles in pounds.

w gross weight of car in pounds.

r= radius of gyration of the car wheels and axles with respect to theiraxis of rotation, in inches.

D car wheel diameter at tread in inches.

As shown by FIG. ,4, most cars exhibit a rolling resistance in a normalrange of 0.15 to 0.4. The gradients for the classification tracks inyard 10, asillustrated by the profile of classification track 22 in FIG.2, are ordinarily selected to accommodate cars of rolling resistancesfalling within the normal range illustrated in FIG. 4. Typically, mostof the length of the trackage in the yard, including the hump yardsection 11A, the'distribution track section 12A, the transitionalclassification track section 24A, and the straight storage tracksections 25A, 25B, and 25C (FIG. 1A) are constructed with a uniformgradient that will assure a relatively safe coupling speed for carsfalling in the normal rolling resistance range of 0. 15 to 0.4 with aminimum of braking by the classification track retarder 26 (FIG. 1). Ina typical yard, the gradients for all of these sections will be of theorder of 0.12 percent, corresponding to a drop T of twelve feet in alength L of one thousand feet. The gradient through the classificationtrack retarder 26, as represented by profile section 26A in FIG. 1A, isusually made slightly greater. For example, the slope of segment 26A maybe of the order of 0.3 percent.

In Classification yard 10, however, each of the classification trackssuch as tracks 21 and 22 is equipped,

with a truck-aligning apparatus for aligning each truck of each car inparallel relation to the straight storage section of the classificationtrack just after the car has left the curved transition section of theclassification track. On classification track 22, this truck-aligningmeans comprises a short car retarder" or aligning device 31 located atthe upper end of the straight storage section 25 of track 22 just belowthe curved transition section 24 of that track. The aligning device 31comprises. two elongated guide rails 32 and33 located on opposite sidesof one rail of classification track 22. The guide rails 32 and 33 do notextend for the full length of a car and are not employed for significantbraking;

hence, they may be much shorter than the conventional 39 foot length foran individual track brake section. However. rails 32 and 33 should belong enough to engage at least two wheels on each car truck. Preferably,the two guide rails 32 and33 of the aligning retarder 31 are of theorder of eight to ten feet long, assuring simultaneous engagement of atleast two wheels on each car truck.

A similar truck-aligning retarder 34 comprising two guide rails 35 and36, is located on classification track 21 at the upper end of thestorage section 28 of that track just below the curved transitionsection 27. A similar truck-aligning retarder is positioned at acorrespondinglocation on classification track 23 and on each of theother classification tracks (not illustrated) in yard 10. Moreover, anadditional short truckaligning retarder 71 is located just ahead of hump70.

- retarder, as when a trim operation is required in classi fication yard10, to enable the passage of trains into and out of the individualclassification tracks without having the retarder in operation. One formof retarder operating mechanism that is quite suitable for thetruck-aligning retarders such as devices 3l'and 34 is that shown in U.S.Pat. No. 3,557,910, to R. W. Wilson, issued Jan. 26, 1971. Inasmuch as.that particular retarder has been manufactured and sold as a commercialunit by Abex Corporation, under the model designations 11-11 and R-llA,and since the mechanism isillustrated and described in theaforementioned u.S. Pat. No. 3,557,910, no detailed description of theretarder apparatus is deemed necessary herein. It should be understoodthat any other relatively, simple and inexpensive normally closedretarder, preferably about eight to feet in length and equipped with asuitable release means, may be utilized for the truck-aligning devices31, 34 and 71.

As shown in FIG. 1A, the grade for the classification track through thesection 31A that includes the trackaligning retarder 31 is increased sothat there is no net braking effect on the cars due to operation of thetruck alignment device. The grade of this short track section 31A ismade somewhat greater than the head removal characteristics of theretarder so that the velocity of the cars moving through the alignmentdevice 31 and down the straight classification track section 25 is notreduced appreciably. In a typical yard, with the gradients set forthabove, the slope for segment 31A may be of the order of 0.6 percent,depending to some extent upon the braking characteristics of theparticular retarder mechanism selected for truck alignment purposes.

FIG. 2 illustrates the effect of the curved transition segments of theclassification tracks on the alignment of the trucks of a typicalrailroad car; and also shows the effect of one of the truck alignmentdevices such as the truck-aligning retarder 31. As shown in FIG. 2, arailroad car 41 passing from the curved transition section 24 to thestraight storage section 25 of classifica-v tion track 22 has the cartrucks canted at a substantial angle to the track rails. Car 41 includestwo trucks 42 and 47. Truck 42 is pivotally mounted on the car at apivot 44, ,the truck having two axles 45 uponwhich the wheels 43 of thetruck are mounted. Similarly, truck 47 is pivotally mounted upon the carat a pivot 48 and includes two axles 49 upon which the wheels 46 of thetruck are mounted. The angle of displacement of trucks 42 and 47 from atrue'parallel relation with the rails of classification track 22 isexaggerated in FIG. 2. However, there is-a definite angular displacementof the car trucks and wheels relative to the rails caused by themovement of the car around the curved track section 24. Moreover, thismisalignment of the car trucks causes a definite increase in thefriction loss at the point of engagement between the wheel flanges andthe heads of the rails. In many instances, this misalignment of the cartrucks is sufficient to produce a marked increase in the rollingresistance of the car as compared with operating conditions in which thecar trucks are accurately aligned in parallel relationship to the rails.

FIG. 2 also shows another car 51 comprising two trucks 52 and '57. Truck52 has already passed through the truck-aligning retarder device 31 andtruck 57 is shown engaged by the truck-alignment retarder. As shown inFIG. 2, the truck-aligning retarder brake rails 32 and 33 have widelyflared endsto admit car wheels that are substantially misaligned withoutproducing the possibility of a derail or other mishap. The wheels 56 onone side of truck 57 are engaged by guide rails 32 and 33 and have beenforced, by the guide rails, into substantially parallel alignment withthe traffic rails of the straight storage section 25 of classificationtrack 22. Truck 52, having already passed through the aligning device31, has its wheels 53 parallel with the classification track. From thepoint shown in FIG. 2, car 51 rolls freely along the storage section 25of track 22, toward brake 26, in the direction of the arrow A. Since thewheels on both trucks 52 and 57 have been engaged by the guide rails 32and 33 of alignment device 31, and the trucks have both beenstraightened relative to the track, the excessive drag introduced bycanting of the car trucks has been eliminated and this rollingresistance factor hasbeen minimized. The same effect will be-attainedwith. respect to car 41 as the car continues its movement down track 22and passes through the truck-aligning retarder 31 on its way to thetrack brake 26 (see FIG. 1).

FIG. 3 affords amore detailed illustration of the car truck 42, movingalong classification track 22 at the upper end of the storage section 25of the track. As shown in FIG. 3, truck 42 is canted with respect to thetwo traffic rails 22A and 22B. As a result of the misalignment of thetruck, two of the wheels 43A and 43D roll freely along the rails but twoof the wheels 43B and 43C have their flanges disposed in draggingfrictional engagement with the heads of the rails 22A and 22Brespectively. The result is a substantial increase in the rollingresistance of the car on which truck 42 is mounted, as described above.

In FIG. 3, truck 42 is shown about to enter a truckaligning device 61that has some of the characteristics of the alignment retarders 31 and34 described in connection with FIGS. 1 and 2 but that is specificallydifferent in that it does not constitute a complete retarder mechanism.Thus, device 61 comprises an elongated guide rail 63, only part ofwhichis shown in FIG/3. The total length of guide rail 63 is preferablyabout eight to ten feet to assure engagement with both of the wheels 43Cand 43D on one side of truck 42. The entrance end 64 of guide rail 63 isflared to a substantial extent to permit entry of wheels that aresubstantially canted with respect to the traffic rails of track 22. Theguide rail 63 is located on the flange side of classification track rail228. Furthermore, the spacing 65 between guide rail 63 and the head 66of rail 22B is narrow enough so that guide rail v63 positively engagesthe flange side of each wheel passing through device 61 if the wheel iscanted to any appreciable extent. I For a conventional guard rail, theflange spacing 65 would be of the order of 1 /8 inch or greater. Foreffective truck alignment operation, however, rail 63 should bepositioned closer to rail head 66, preferably with a spacing 65 of about1% to 1% inches. If the wheels 43C and'43D on truck 42 are alreadysubstantially parallel to rail 228, the guide rail 63 has little or noeffect on the wheels; with the usual flange depth of approximately Weinch, the fianges on the wheels pass alongside rail '63 withoutsubstantial braking and with'no change in truck orientation. With thewheels on truck 42 canted as shown, however, the guide rail 63 forceswheels 43C and 43D into parallel alignment with rail 22B, turning truck42 about pivot 44 and reducing the rolling resistance of the carattributable to misalignment of the truck because the entire truck isstraightened up as wheels 43C and 43D are re-aligned.

As in the case of the retarder aligning devices 31 and 34, the gradethrough the track segment covered by guide-rail 63 should be madesomewhat greater than the normal incline for the yard to compensate forany friction loss that may occur as the car wheels move through thealigning device. Guide rail63 may be or rigid construction.Alternatively, guide rail 63 may be mounted for quite limited movementin a direction toward and away from the traffic rail 22B (arrow B), withone or more large springs or other resilient mounting meansurging theguide rail toward the head 66 of the traffic rail and allowing some giveas the t'ruck'42 moves through the alignment device 61.

Cars entering classification yard 10 frequently must traverse curvedtrack in the approach to hump 70, skewing the car tracks in the samemanner as described above with respect to-the curved track segments inthe yard itself. For optimum efficiency in operation of the yard, eachcar or cut of cars leaving the hump should be restored to maximumrollability. To this end, the car-aligning device 71 is positionedimmediately ahead of. the yard hump and is employed to straighten thetrucks on each car as the car enteres the yard. Device 70 may comprise ashort retarder of limited braking effect, like device 31, or aclose-coupled guide rail apparatus like device 61, imposing only alimited additional .load on an engine pushing the cars to the top of theployed are relatively simple and inexpensive, and re-' quire a minimumof maintenance.

I claim:

l. The method of improving the rollability of railroad cars duringclassification operations in a railroad classification yard, in whichindividual cars or cuts of cars are released from a hump location toroll, by gravity, down an inclined hump track and thence down aclassification track including a transition section comprising at leastone curve leading into a straight storage section, said methodcomprising positively engaging at least two wheels on each truck of eachcar. simultaneously, to align each truck inparallel relation to saidstorage section of said classification track, without appreciablebraking of the car, after the car has completely traversed saidtransition section of said classification. track and before the car hasmoved any substantial distance down the straight storage section of saidclassification track. 1

2. The method of improving car rollability, in operation of aclassification yard, according to claim 1, comprising the further stepof positively and simultaneously engaging atleasttwo wheels on eachtruck of each car, as the car approaches the hump location, to aligneach truck parallel to the hump track prior to release of the car toroll down said hump track.

3. In a gravity-operated railroad classification yard of the kindincluding a hump, a hump track extending over and inclined downwardlyfrom said hump, a plurality of classification tracks connected to andinclined downwardly from said hump track, each classification trackcomprising a curved transition .section leading into a straight storagesection, and retarder means for I braking each car as the car traversessaid yard between said hump and the storage section of one of saidclassification tracks, the improvement comprising: a plurality of truckaligning means, one located at the upper end of the storage section ofeach classification track, for aligning each truck of each car inparallel relation to the storagesection of the associated classificationtrack without appreciable braking of the cars, eachsaid truck aligningmeans comprising an elongated guide rail, long enough to engage at leasttwo wheels on each car truck, positioned parallel to the flange of onerail of 'said classification track and close enoughto saidclassification track to engage the flange side of each car wheeltraversing said classification track at any appreciable angle ofmisalignment relative thereto, the downward inclination of said storagesection of each classification track, in the portion thereof extendingthrough said truck aligning means, being somewhat in excess of the headremoval characteristics of said truck aligning means.

4. A gravity-operated railroad classification yard according to claim 3,in which the length of said guide rail is of the order of eight to tenfeet.

5. A gravity-operated railraod classification yard according to claim 3,in which said truck aligning means further comprises a second elongatedguide rail, said guide rails being parallel to each other and located onopposite sides of said one rail, and means urging said guide railstoward each other to engage both sides of the wheels on each car truckpassing through said aligning means.

6. A gravity-operated railroad classification yard according to claim 5,in which said truck aligning means further comprises release means forseparating said guide rails to allow free passage of car wheelstherethrough. r

7. A gravity-operated railroad classification yard according to claim 3,in which said truck aligning means further comprises resilient meansurging said guide rail toward engagement with said wheels.

tional truck aligning means, positioned on said hump track ahead of saidhump, for aligning each truck of each car parallel with said hump trackbefore the car 8. A gravity-operated railroad classification yard ac- 5is released to roll into the y

1. The method of improving the rollability of railroad cars duringclassification operations in a railroad classification yard, in whichindividual cars or cuts of cars are released from a hump location toroll, by gravity, down an inclined hump track and thence down aclassification track including a transition section comprising at leastone curve leading into a straight storage section, said methodcomprising positively engaging at least two wheels on each truck of eachcar, simultaneously, to align each truck in parallel relation to saidstorage section of said classification track, without appreciablebraking of the car, after the car has completely traversed saidtransition section of said classification track and before the car hasmoved any substantial distance down the straight storage section of saidclassification track.
 2. The method of improving car rollability, inoperation of a classification yard, according to claim 1, comprising thefurther step of positively and simultaneously engaging at least twowheels on each truck of each car, as the car approaches the humplocation, to align each truck parallel to the hump track prior torelease of the car to roll down said hump track.
 3. In agravity-operated railroad classification yard of the kind including ahump, a hump track extending over and inclined downwardly from saidhump, a plurality of classification tracks connected to and inclineddownwardly from said hump track, each classification track comprising acurved transition section leading into a straight storage section, andretarder means for braking each car as the car traverses said yardbetween said hump and the storage section of one of said classificationtracks, the improvement comprising: a plurality of truck aligning means,one located at the upper end of the storage section of eachclassification track, for aligning each truck of each car in parallelrelation to the storage section of the associated classification trackwithout appreciable braking of the cars, each said truck aligning meanscomprising an elongated guide rail, long enough to engage at least twowheels on each car truck, positioned parallel to the flange of one railof said classification track and close enough to said classificationtrack to engage the flange side of each car wheel traversing saidclassification track at any appreciable angle of misalignment relativethereto, the downward inclination of said storage section of eachclassification track, in the portion thereof extending through saidtruck aligning means, being somewhat in excess of the head removalcharacteristics of said truck aligning means.
 4. A gravity-operatedrailroad classification yard according to claim 3, in which the lengthof said guide rail is of the order of eight to ten feet.
 5. Agravity-operated railraod classification yard according to claim 3, inwhich said truck aligning means further comprises a second elongatedguide rail, said guide rails being parallel to each other and located onopposite sides of said one rail, and means urging said guide railstoward each other to engage both sides of the wheels on each car truckpassing through said aligning means.
 6. A gravity-operated railroadclassification yard according to claim 5, in which said truck aligningmeans further comprises release means for separating said guide rails toallow free passage of car wheels therethrough.
 7. A gravity-operatedrailroad classification yard according to claim 3, in which said truckaligning means further comprises resilient means urging said guide railtoward engagement with said wheels.
 8. A gravity-operated railroadclassification yard according to claim 3, and further comprising anadditional truck aligning means, positioned on said hump track ahead ofsaid hump, for aligning each truck of each car parallel with said humptrack before the car is released to roll into the yard.